Most of your queries have been answered by our "flabbergasted" Jay. I must say I'm also "struck", but having known you for a while I knew you'd not resist the temptation to give ICS a spin.

I'm not sure about the inbuilt software, but tether is built-in on all, unless Big Red has adulterated the system. Probably.
I see you've figured screenshot. On the Note its different: all I have to do is swype the screen with the palm of my hand...

Here is what I find indispensable in apps for me:

First the Launchers. ADW or Go Launcher ADW is better imo opinion, but Go launcher, is more pleasant. You can add the Go Locker, to change your lock screen, which is great.There is SPB Shell 3D. Very eye catching, some unique widgets, but hogs memory a bit.